Another approach would be:
SELECT CASE Level
CASE < 80 : HIGH Pump1 : LOW Pump2 : LOW Pump3 : LOW Pump4
CASE < 70 : HIGH Pump1 : HIGH Pump2 : LOW Pump3 : LOW Pump4
CASE < 60 : HIGH Pump1 : HIGH Pump2 : HIGH Pump3 : LOW Pump4
CASE ELSE : HIGH Pump1 : HIGH Pump2 : HIGH Pump3 : HIGH Pump4
END SELECT